Ideas to Improve Son's Handwriting.....

I think you need to talk to his teacher. I am sure they have helpful tips for helping left handed children learn how to form letters accordingly. Tracing letters has helped my youngest a great deal. I know there is a specific way of handwriting at least in our school district. Not how I would write so I would get that information from his teacher. They can offer tools and resources and should for you.
Also, don't critique his hand writing but labeling it "neat", just mention that sometimes you aren't sure what he wrote and could he re write it.

Kids are super sensitive at this age and feeling pressure as it is, being left handed puts him at a disadvantage unless he is getting help in class with forming letters correctly as they want to see it. He will have to learn a different way but that doesn't mean his way is wrong. All of this should be occuring in class with learning to write well, complete sentences neatly and so on. At least that is what my daughter is learning. Proper spelling, capitolization, punctuation and so on.
I have a second grader so I understand.

Just call his teacher and make a time to see her.
A lot of "men" never learn to write neatly, it is what the teacher thinks is reasonable you should gauge his progress to.

I am a lefty and I don't think that your son's teacher is helping him any by "laying off" him when she finds out he is a lefty. There should be alternative strategies that they can teach him and still use their handwriting books....like the angle of his paper, the way that he holds the pencil. It could be that the pencil is too small around and he needs a pencil grip. I agree that handwriting is important but it shouldn't matter that your son is a lefty....it should be treated like any other learning difference. Talk to the teacher about the style of writing that they are using at his school and if their are tips for lefties that might make it easier. Keep trying.

Improving his fine motor skills will help to improve his handwriting. Find all of your old Christmas cards, birthday cards, etc, use a hole punch to put holes all along the edges, and then have him "sew" on the cards with yarn, you can also cut up cute cereal boxes, tissues boxes, or whatever other cardboard scraps you have and do the same with those. Another good idea is to give him a thumb tack or a pin and have him poke holes in a paper to make pictures, he can do this free hand or poke holes along the lines a picture or words. He can also string beads to make necklaces to give to his teachers, grandmas, mom, etc. When he starts to get more proficient at these activities, start teaching him to sew by hand, just cut out two squares of fabric for him to sew together to make a pillow.

Please see my website for left-handed children: www.lefthandedinfo.com

Updated

My website could really help you www.lefthandedinfo.com

The other thing that comes to my mind is to help him build his finger muscles and control.
Play dough, floam, clay, working with small beads, building toys with the small screws etc....
Practicing with the mazes, tracing letters in a shallow pan in salt, shaving cream/whip cream., finger paint on a cookie sheet..etc...

My 8 year old, almost 9, has been identified with SPD, Sensory Processing Disorder, along with dyspraxia and motor planning issues so writing was very difficult for him. Some of the methods that helped my son I think would help yours based on what you are describing.

http://www.proedinc.com/customer/productView.aspx?ID=577

The above is a link to a website to buy some paper that has raised lines on it---as your son writes he can feel the raised line under his hand and it will help with the "bigger and bigger" that you describe. It is costly but feasible that by the time he is through with the package you will see improvement.

There is a program called Handwriting Without Tears. There are many DCSD elementary schools that incorporate in the Kindergarten curriculum. My son received instruction with this through his IEP and the school OT. I feel certain you could purchase this program and do it as a home study course for your son.

Take a cookie sheet and fill it full of a clay like Sculpy (Michaels has it). Press it out like you are making cookie bars and have him write letters/draw in it with a skewer/pencil---you could draw boundary lines to help his size and it would be fun and different. (Sculpy because it doesn't dry out.)

Consider having him evaluated for fine motor issues if these things don't help. Other problems he may have associated if fine motor were a problem, other than writing, would be problems with cutting out patterns on a line or manipulating small objects/small puzzle pieces.

My son's handwriting as a 3rd grader is typical and he receives good grades in his handwriting---I have to know it's because of the extra work he put in.

Hope this helps and best wishes.

definitely handwriting without tears !

I am a kindergarten teacher, and I know what a headache handwriting can be. I heard one teacher saying that they used a very small pencil for kids who were having trouble. Kind of like a golf pencil. See if that helps. When he's writing at home, have him practice circling the words (it's hard to do without spaces). Also, practice rereading his work to him and show him that you'd love to read all his smart thinking, but it's hard to do if he doesn't write neat or if there are no spaces. Tell him you want so badly to be able to read his writing. Maybe even give him to task to write a letter telling you about what he'd like you to buy at the grocery store, and tell him that one reason it's important to write neat is so OTHERS can read your writing and respond appropriately. I hope that makes sense. Writing is such an important thing to me, and I'd hate to see your son not like writing because of neatness. Let me know if you have any other questions about this, maybe I can help.